Leaders of the MS-13 gang Heriberto Martinez, left, and Carlos Ortega, right, are scheduled to go on trial in federal court in Central Islip. (Credit: Handout)

Two leaders of the MS-13 street gang are scheduled to go on trial Monday in federal court in Central Islip in connection with a series of five killings over six weeks, including that of a mother and her 2-year-old son.

The killings, which all occurred in 2010, include that of a security guard at a bar because he had attempted to stop gang members from leaving without paying their tab; a man...

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Two leaders of the MS-13 street gang are scheduled to go on trial Monday in federal court in Central Islip in connection with a series of five killings over six weeks, including that of a mother and her 2-year-old son.

The killings, which all occurred in 2010, include that of a security guard at a bar because he had attempted to stop gang members from leaving without paying their tab; a man who was believed to be a member of a rival gang; and a fellow MS-13 member who was hacked and stabbed to death with a machete and knives because he refused to kill a rival gang member, officials have charged.

The defendants, Heriberto Martinez, 25, of Far Rockaway, and Carlos Ortega, 23, of Brentwood, have pleaded not guilty to murder and other charges. They both were active in an MS-13 clique, or chapter, in the Brentwood area, according to officials.

The cases are the latest resulting from a decade-old war against Long Island street gangs by the FBI's Long Island Gang Task Force, which have included agents, local police and correction officers and other federal personnel.

Since the task force founding in 2003, agents working together with local law enforcement have arrested 850 gang members or associates, according to FBI spokesman James Margolin. In addition to MS-13, the gangs involved included the Latin Kings, the Bloods, the Crips, the 18th Street, the Netas and SWP.

Of those arrested, 516 have been convicted of various crimes, including murder, attempted murder, narcotics trafficking, extortion and witness tampering, Margolin said. The others are still in various stages of the legal process, he said.

Despite the arrests and convictions, experts say that the gang problems and gang-initiated violence will continue to ebb and flow on Long Island.

Richard Donoghue, who prosecuted many of the gang cases as the former head of the U.S. attorney's office on Long Island and who is now senior vice president for litigation at CA Technologies in Islandia, said that "gangs are constantly recruiting from Central America and in the United States."

Donoghue said a series of arrests usually leads to a drop in gang activity and violence. But then the gangs rebuild and the cycle begins again.

In the latest federal gang trial, Martinez is accused of ordering the Feb. 5, 2010, slaying of the mother, Vanessa Argueta, 19, of Hempstead, and of a being an accessory after the fact in the murder of her son, Diego Torres, 2. The toddler was shot twice in the head; his mother once in the head and once in the chest, court papers said.

The former boyfriend and two other gang members ostensibly told Argueta that they wanted to take her to a restaurant. But she could not get a baby-sitter for Diego, so the toddler went along. Mother and child were driven to a wooded area of Central Islip where Argueta was first shot to death and then the 2-year-old, after he "began crying" and hugged the leg of one of the killers, court papers say.

Because mention of the killing of a 2-year-old is considered too prejudicial to Martinez, jurors will be told only that one of the victims was named DiegoTorres without stating his age or relationship to Argueta, officials said.

Martinez is also accused of taking part in the March 6, 2010, death of Nestor Moreno, 22, a guard at a Hempstead bar, a few weeks after he had unsuccessfully attempted to stop Martinez and other MS-13 members from leaving without paying their bill.

Ortega is charged with the Feb. 17, 2010, slaying of David Sandler, 20, in Brentwood because MS-13 members thought he belonged to the rival Latin Kings gang.

Both Martinez and Ortega are charged in the March 17, 2010, killing of Mario Alberto Quijada, 25, of Far Rockaway, who was slashed and knifed to death on a Far Rockaway beach because he did not have enough "heart" to take part in the killings of rival gang members, court papers say.

Several other MS-13 members also have been arrested in those killings and have either pleaded guilty or are awaiting trial.

Martinez's lawyers, Elizabeth Macedonio of Bayside, and Arnold Levine of Manhattan, declined to comment, as did Ortega's lawyers, Ira London of Manhattan and Marianne Rantala of Commack. Eastern District federal prosecutors John Durham, Raymond Tierney and Carrie Capwell, also declined to comment.

The trial is expected to last six weeks before U.S. District Judge Joseph Bianco. If convicted, Martinez and Ortega face life in prison.